Studies of RF Shimming Techniques with Minimization of RF Power Deposition and Their Associated Temperature Changes.
Studies of RF Shimming Techniques with Minimization of RF Power Deposition and Their Associated Temperature Changes.
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DOI：
10.1002/cmr.b.20185
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发表时间：
2011-02
影响因子：
0.9
通讯作者：
Ibrahim, Tamer S.
中科院分区：
文献类型：
--
作者：
Tang, Lin;Hue, Yik-Kiong;Ibrahim, Tamer S.
关键词：
在超高频（UHF）场中，人体磁共振成像（MRI）关注与超高频（UHF）场的均匀性有关的问题。 场[负责激发自旋的射频（RF）磁场分量]和局部/平均比吸收率（SAR）非常明显。在这项工作中，通过RF匀场技术，将耦合RF线圈和负载（18组织解剖学详细的人类头部模型）视为单个系统的全波电磁模型被用于同时改善 场的各个区域的利益在整个体积的人的头部，并尽量减少总射频功率沉积在7和9.4 T。数值结果表明， 在定向和尺寸不同的3D厚片中、在大脑中以及在整个头部体积中，场均匀性（由方差系数评估）可以得到极大的改善，而不会将头部中的总RF功率沉积增加到超过利用正交激励获得的功率沉积。使用配备发射阵列激励系统的7 T人体MRI扫描仪，在头部大小的体模上对RF匀场模拟结果进行了实验验证（通过在没有实验B1测量的情况下执行RF匀场）。计算并比较了正交和RF匀场激励条件下的SAR和相关温度变化。
In ultrahigh field (UHF), human magnetic resonance imaging (MRI) concerns related to the homogeneity of the field [the radiofrequency (RF) magnetic field component responsible for the excitation of the spins] and the local/average specific absorption rate (SAR) are highly evident. In this work, through RF shimming techniques, a full-wave electromagnetic model that treats a coupled-RF coil and the load (an 18-tissue anatomically detailed human head model) as a single system is utilized to simultaneously improve the homogeneity of field in various regions of interest across the volume of the human head and minimize the total RF power deposition at 7 and 9.4 T. The numerical results illustrate that the field homogeneity (evaluated by the coefficient of variance) can be greatly improved in 3D slabs that vary in orientations and sizes, in the brain, and in the entire head volume without increasing the total RF power deposition in the head to exceed that obtained with quadrature excitation. The RF shimming simulation results are experimentally validated (by performing RF shimming without experimental B1 measurements) on a head-sized phantom using a 7-T human MRI scanner equipped with a transmit array excitation system. The SAR and associated temperature changes under quadrature and RF shimming excitation conditions are calculated and compared.
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影响因子：
3.3
作者：
Abraham, Roney;Ibrahim, Tamer S.
通讯作者：
Ibrahim, Tamer S.
影响因子：
3.2
作者：
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通讯作者：
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影响因子：
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作者：
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影响因子：
3.3
作者：
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影响因子：
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作者：
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通讯作者：
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